ƒand " flash modes
Adjustment factors for other ISO film speeds
ISO film speed | 25 | 50 | 200 | 400 | 800 | 1600 |
Factor | x 0.5 | x 0.71 | x 1.4 | x 2 | x 2.8 | x 4 |
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For film speeds other than ISO 100, multiply the guide numbers by the factors shown in the above table.
For example, if the film speed in the previous example was ISO 400 rather than ISO 100, the guide number is 72 (36 x 2).
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